Corona Electrode Research Articles

Shotcreting with Cement–Sand Mixtures Under the Influence of an Electrostatic Field

One of the primary and still unresolved problems of shotcreting is the high rebound rate of the material, which reaches over 20% in “dry” shotcreting. There is a practical need to improve the very principle of shotcreting and methods for optimizing the movement of torch particles. Materials and Methods: The purpose of this study was to justify the use of the electrostatic treatment of cement–sand mortar in the process of performing shotcreting works using the dry method. It was proposed that the binder and then the finished mixture be ionized step-by-step (by passing it through a non-uniform electrostatic field formed by corona electrodes). As a result, the shotcrete will be held on the fence. Results: Analysis of the modeling results shows that the presence of an electrostatic field slows down the particle and reduces the kinetic energy of the rebound. After theoretical calculations, experiments were conducted, during which, the torch size and the plant productivity were changed, and the rebound mass was weighed. After application to the surface, prototypes were formed and subjected to strength tests. It was determined that gunning in a sharply non-uniform electric field demonstrates its practical and economic efficiency due to the uniform deposition of charged particles on the treated surface and low power consumption. Conclusions: It was established that the electrostatic treatment of a cement–sand mixture during application allows concrete particles to be retained on the shotcrete surface, the rebound of the material to be reduced and the strength of concrete to be increased.

Analysis of electric filters for cleaning the air environment of production premises

RELEVANCE: The problem of hazardous working conditions in Russia attracts attention due to an increase in the proportion of workers exposed to negative impacts on their health. Of particular interest is the analysis of the air environment as the main factor influencing human health. 32.2% of workers in hazardous working conditions are exposed to airborne factors, which leads to occupational diseases. To reduce the harmful effects of the air, it is necessary to clean it from harmful components. A promising device for air purification is an electric precipitator.PURPOSE: The study is aimed at selecting and optimizing electric precipitators for air purification in industrial premises. The goal is to determine the most effective design of an electric precipitator for cleaning the air environment of industrial premises.METHODS: The analysis is carried out on the basis of statistical data, the results of studies of electric precipitators of various designs for cleaning the air from dust, harmful gases and microorganisms. The results are used for comparative analysis.RESULTS: The study reveals that different designs of electrostatic precipitators demonstrate different effectiveness in air purification depending on the type of design. The design of corona electrodes affects ozone generation. It has been established that two-zone electrostatic precipitators with needle corona electrodes on the negative corona can significantly reduce ozone emissions. Wet electrostatic precipitators have regeneration, and the presence of several stages increases the cleaning efficiency. Electrostatic filters do not generate ozone and can be used in explosive low-volume areas.CONCLUSION: The study confirms that the choice of electrostatic precipitator should depend on the specifics of production and the volume of the room. For explosive environments, electrostatic precipitators should be preferred, while for large areas, a wet multi-stage electrostatic precipitator is recommended. Electrostatic precipitators-ozonizers can be effective for air disinfection. Summarizing the results allows us to conclude that it is important to choose the appropriate type of electrostatic precipitator to ensure optimal air conditions for the safety of workers.

Drop-On-Demand Microdroplet Generation under Charge Injection by Corona Discharge.

In printing, microreactors, and bioassays, the precise control of micrometer-scale droplet generation is essential but challenging, often restricted by the equipment and nozzles used in traditional methods. We introduce a needle-plate electrode corona discharge technique that injects charges into an oil layer, enabling the precise manipulation of droplet polarization and splitting. This method allows for meticulous adjustment of microdroplet formation regarding location, size, and quantity by modulating the discharge voltage, discharge time, and electrode positioning. It enables the immediate initiation and cessation of droplet production, thereby facilitating on-demand droplet generation. Our study on the voltage-dependent droplet stretch coefficient shows that as the voltage increases, the droplets transition from controlled splitting to regular Taylor cone-like ejections, eventually reaching the Rayleigh limit and fully breaking apart. These advancements significantly improve microfluidic droplet manipulation, offering considerable benefits for applications in targeted drug delivery, rapid disease diagnostics, and precise environmental monitoring.

Ionization Processes of Negative Corona Discharge Part 1. Review and Experiment

The purpose of the research is an experimental study of physical processes in the near-electrode zones of negative point electrodes in an electronegative gas (air) under the condition of a high-voltage field.Methods. Video image analysis, current-voltage characteristics measurements, and spectroscopy are used. The current-voltage characteristics of the corona discharge ignition voltage in the environment are measured, the problem of experimental identification of surface charges, the mechanism of negative corona discharge ignition, and the ionic structure of streamers is studied, degradation of electrodes during negative corona discharge, spectrum of corona discharge creation and electromagnetic sound.Results. It is shown that at small radii of curvature of needle electrodes, the development of a negative corona discharge is due to the cold emission of electrons, and on flat and slightly curved negative electrodes, due to the capture of surface electrons by electron-withdrawing molecules. The mechanism of ignition of a corona discharge in an electronegative gas with a negative needle, the structure of streamers from negative needles, the emission spectrum and ethonic degradation of electrodes have been studied.Conclusions. The ignition of a negative corona discharge at small radii of the tips of the pointed needles (ro less than tens of microns) is due to the cold emission of electrons followed by impact ionization of neutral molecules. With slightly curved electrodes, the appearance of a negative corona discharge is due to the capture of surface electrons by electronegative gas molecules with subsequent plasma-chemical reactions. The formation of surface electrons depends on many factors: the presence and structure of oxide films (roughness, defects, etc.), which determine the electron work function and form local fields at the tips of microtips. The appearance of a corona discharge leads to degradation of the corona electrodes, expressed in the spraying of the tips of the points and the melting of the needles. In the dark region of the negative corona discharge (U < U*), photons in the in the ultraviolet spectrum (UV spectrum) are emitted, and when U > U*, in addition to UV photons, photons in the visible region of the spectrum are emitted. Glow fluctuations are caused by the chaotic dynamics of the formation of injection centers (melted tubercles - ectons) on the surface of the corona electrode. The ignition of a corona discharge is accompanied by sound emission with a frequency of about 300 Hz.

A NUMERICAL ANALYSIS ON THE SUBMICRON- AND MICRON-SIZED PARTICLE SEDIMENTATION IN A WIRE-TO-PLATE ELECTROSTATIC PRECIPITATOR

Electrostatic precipitators (ESPs) are frequently utilized in collecting fine organic and inorganic materials from continuous liquid with few moving parts and high efficiency using electrically charging the particles. In this study, cross-sectional 2D geometry of a wire-to-plate electrostatic precipitator the parametric data of which originally published elsewhere was numerically modeled and validated to investigate submicron-micron particle charging in terms of diffusion and field charging mechanisms and precipitation behavior of particles with detailed electric field properties. Electric field, gas flow, and particle trajectory equations are coupled and solved in a multiphysics solver. Particle tracking is realized with the Lagrangian approach. Results indicate variations in electric field strength and space charge density between corona electrodes, with space charge present in the entire precipitation channel. Between two different charging mechanisms, diffusion charging prevails for charge accumulated on submicron particles, whereas field charging becomes dominant for particles larger than 1μm diameter. However, for the ESP configuration considered in this study, particles reach a charge saturation in less than 0.7 seconds, regardless of their size. Although calculated precipitation efficiencies for micron-sized particles can reach to 100%, efficiencies for submicron particle range drop with increasing particle size, as diffusion charging rapidly loses its effectiveness, in 50-250nm range.

Investigation of the electret properties of PDLA/PEC porous composite films

In the present paper the influence of both time and low pressure on the surface potential decay of porous composite films of poly(D-lactic acid) and poly(ε-caprolactone) was investigated. The samples were charged in a corona discharge by means of a corona triode system under room conditions. Positive or negative voltage was applied to the corona electrode and voltage of the same polarity as that of the corona electrode was applied to the grid. After charging, the initial surface potential was measured using the method of the vibrating electrode with compensation. Two groups of tests were performed. In the first group, after charging, the electrets were placed into a vacuum chamber where the pressure was reduced step by step in the range from 1000 mbar to 0.1 mbar. At each step the samples were stored for 1 minute. After that the electrets were removed from the vacuum chamber, their surface potential was measured again and the normalized surface potential was calculated. The influence of low pressure was analyzed by the equation that describes processes of desorption from the electret’s surface. In the second group, after charging, the electret surface potential was measured by the time of storage. The possible surface potential decay mechanisms responsible for the electret’s behavior were discussed. It was established that the surface potential decay depends on both corona polarity and type of films. It was shown that the samples charged in a positive corona are more stable than those charged in a negative corona.

Silindir-Düzlem Korona Elektrot Sisteminin Koşulsuz Optimizasyonu

In this study, based on the Newton-Raphson method, the unconditional optimization of the “thin cylinder-plane” corona electrode system of high-voltage devices with a non-uniform or weakly uniform electric field, widely used in various technological processes of electron-ion technology, is analyzed. For this purpose, the condition of a self-sustaining electric discharge was used for the electrode system under consideration.

Numerical study of the influence of using crenelated collecting plates on the electrostatic precipitators

Electrostatic precipitators (ESPs) are extensively used in industry to remove undesirable particles from flue gases using corona discharge. The particle collection efficiency of the ESPs is greatly affected by the optimization of collecting plates and corona electrode configurations. Different researchers are working to improve standard models in various ways to obtain a better performance of ESPs. This paper investigates the influence of using crenelated plates (CrPs) with five designs of collecting electrodes by changing the geometries of the crenelated part (the amplitude and the wavelength) and comparing them with flat plates (FPs) on the electrical proprieties of a single-stage ESP. The particle collection efficiency of the ESP and the dust particles’ transport behavior were enhanced using the crenelated collecting plates (CrPs), especially when using case E, which provides the highest collection efficiency for all particle sizes (0.01-5) μm. For instance, the particle collection efficiency of the CrP E type is 76%, which is 8% higher than the CrP D type for particles of about 0.1 μm. At the same time, 88% for CrP E with 0.05μm, which is 10% greater than the CrP D type. In addition, the influence of changing the amplitude (A) has more significant than changing wavelength (λ) on the particle collection efficiency and the dust particles’ transport behavior.

A Novel Energy Harvesting Method for Online Monitoring Sensors in HVdc Overhead Line

Due to the lack of alternating electric fields and alternating magnetic fields in HVdc transmission system, there has been no sustainable and stable energy harvesting method compatible with them up to now, hindering the application of HVdc sensors. In this letter, we proposed a novel dc energy harvesting method using corona current, and an energy harvesting circuit is constituted with space ion flow generated by dc corona. The feasibility of the proposed method is increased by adding an artificial corona electrode and placing the load before the corona electrode. In addition, it can flexibly operate at any position in an HVdc transmission system according to actual demand. Then the output power is further maximized by adopting a capacitor with high working voltages. The detailed measurement results based on the experimental system validate the effectiveness of the proposed method, with a stable output power as high as 10.15 mW in a dc system of 22 kV. A detailed discussion of the overall performance is finally carried out.

Surface electric charge decay behavior of Polypropylene (PP) films treated by atmospheric air dielectric barrier discharge

Atmospheric air dielectric barrier discharge (DBD) is one of the most effective physical techniques for the cold plasma source. It is a promising technique used to modify the surface properties of polymers. This modification leads to improving wetting and adhesion properties, a change in surface roughness and other significant technological features. In recent studies, researchers have showed that DBD plasma exposure can modify the electric properties of insulating materials. In this study, we focused our attention on the influence of DBD plasma treatment on the surface electric charge behavior in polypropylene (PP) thin films. The effect of DBD plasma has been studied as a function of treatment time for two values of applied discharge voltages; 7 and 12 kV. After being exposed to DBD plasma, the samples were charged for 5 seconds in ambient air using a negative triode corona electrode system. The influence of DBD plasma treatment on the surface electric charge behaviour in PP thin films was investigated. The surface characterization of the untreated and treated PP films is performed using surface electric charge decay measurements, for identical charging conditions.

Experimental Research on a Needle Roller-Type Electrostatic Separation Device for Separating Unginned Cotton and Residual Films

In the mechanized harvesting of cotton in Northwest China, problems result from the presence of a residual film, and it is difficult to remove the residual film in the cotton processing stage. In this study, a needle roller electrostatic separation device was designed for use with unginned cotton residual films, and a series of experiments was carried out. Through force analyses and charge testing of the seed cotton and the residual film, a theoretical basis was provided for separating them. Taking the residual film separation rate as the response index, the optimal parameter combination was determined with a response surface analysis of three factors and three levels, and a mathematical model was established. The test results showed that the optimal parameter set included a 25.3° corona electrode angle, a 172.3 mm corona electrode distance, and a 5.25 W discharge power. After optimization of the parameters for separation, the average residual film separation rate was 91.7%. This research provides data and technical support for the design of the machinery and the selection of the parameters used in treating machine-picked cotton and separating the residual film.

Enzyme activity of β-galactosidase immobilized in polyelectrolyte multilayers deposited on corona charged composite substrates

In the present paper chitosan and xanthan polyelectrolyte multilayers (PEMs) deposited on composite multicomponent poly(D-lactic acid) (PDLA) / poly(ε-caprolactone) (PEC) substrates were investigated. The substrates' melting phenomena and degree of crystallinity were investigated by differential scanning calorimetry (DSC). Based on the melting behaviour it was suggested that PLA and PEC are not miscible at molecular level and no co-crystallization is realized. The substrates obtained were charged in a corona discharge. Positive or negative 5 kV voltages were applied to the corona electrode and 1 kV voltage of the same polarity - to the grid. The normalized surface potential dependences on the storage times were investigated. The results obtained show that the values of the normalized surface potential decay faster for negatively charged substrates. Layer-by-layer (LbL) technique was used for multilayer deposition on the substrates. PEMs with 8 layers were obtained. The enzyme of β-galactosidase was immobilized in the obtained polyelectrolyte multilayers. The enzyme activity of the immobilized enzyme was studied. The experimental results obtained show that the enzyme immobilization in positively charged films have higher activity compared to the negatively charged ones, independently of substrates type.

Research on Wire-to-Two Fin Configuration for Positive Atmospheric Plasma by Electrokinetic Blower

Interest in the development of electro-fluid-dynamic devices (EFDs) based on corona discharge is growing due to their advantages and applicability across different industrial sectors. On the one hand, their performance as forced convection motors, in terms of weight, volume, and absence of noise and moving parts, make them competitive against traditional systems such as fans. On the other hand, the actions of the corona discharge, in terms of elimination of viruses and bacteria, are already known. This paper studies the characteristics of corona discharge in terms of air flow for a new proposed configuration and geometry of electrodes. A systematic study is performed through a parametric study of the distances, power consumption, and size of the corona electrode. The characteristic voltage–current (CVCCs) and flow–pressure curves obtained provide design rules to use the generated corona discharge and the device itself, as a silent air propeller, which may also sterilize the surrounding environment and surfaces.

Study and Numerical Simulation of Negative and Positive Corona Discharge: A Review

Two models to describe the phenomenon of corona discharge are presented: the first is known as the plasma model which with plasma chemistry defines the volumetric and surface reactions among charge carriers such as electrons, positive, and negative ions. This model uses Poisson's equation and a formulation of the space-charge density to calculate the electric field necessary to solve the species transport equations. Besides, only the plasma model determines the density of the charge carriers. The second is a simplified model which describes the corona discharge in terms of current conservation coupled with Poisson's equation. This model does not have any connection with the attributes of plasma chemistry. Both models propose solutions for the electric potential and space charge density distribution from the corona electrode to the ground electrode.

Experimental Characterization of a Tri-Needle-Type Corona Electrode in View of Improving Charging Uniformity

Experimental Characterization of a Tri-Needle-Type Corona Electrode in View of Improving Charging Uniformity

The Effect of Corona Wire Position and Radius in a Duct-Type ESP with Wavy Collecting Plates

Electrostatic precipitators (ESPs) have become one of the most effective methods for removing harmful particles from various industries. Many investigations in this subject are constantly developing due to the inherent benefits of using an ESP, and there are many robust initiatives taking place today all over the world. Different configurations of collection and discharging electrodes must be investigated to improve the ESP performance of ESPs. Many studies are working to enhance existing models in different ways. The geometry of the electrodes and the collecting plates is one area that could be improved. This paper investigates the wavy designs of collecting electrodes with varied corona electrode radius (range of variable corona radius (0.07-0.6 mm)) and position in a single-stage ESP. Wavy plates (WPs) and Inverted wavy plates (InvWPs) are compared to flat plates (FPs) using a numerical simulation tool. The results of this work show the impact of changing the corona radius when wavy and inverted wavy collecting electrodes are used on the electric potential, electric field strength, current density, and space charge density distribution, and particle collection efficiency. When compared to InvWPs and FPs, WPs show the highest performance in this range of particles. Although InvWPs can be utilized to reduce current density or space charge density, they do not increase particle collection efficiency.

Modelling the Role of the Inner Electrode Radius on the Oxygen Negative Corona Discharge in Coaxial Electrode Geometry

The charge species plays a vital role in changing the field in direct current discharge (DC). This article introduces a numerical modeling in one dimension of the inner electrode diameter of oxygen-fed negative corona discharge in coaxial electrodes geometry. The properties of negative corona plasma in a concentric cylindrical electrodes (wire-cylinder) were simulated by COMSOL Multiphysics software. Various diameters of negative corona electrode, namely 0.01, 0.025, 0.05, 0.075, and 0.125 mm, were applied, ​​where the diameter of the outer cylindrical electrode was taken as 15 mm. The model was run at atmospheric pressure and the applied negative voltage was -10 KV. Moreover, oxygen gas was used to fill the inter-electrodes distance. Furthermore, the spatial distribution of electrons, positive ions, and negative ions as a function of the diameter of negative electrode of the negative corona discharge were investigated. The study also tested the effects of the electrode diameter of the negative corona discharge on ozone generation. The observed decrease in ozone density with the increase in negative electrode diameter was reasonable and consistent with other results provided by researchers in this field.

Experimental characterization of electric potential uniformity at the surface of polymer plates corona charged by multiple-row needle-type electrodes

Diverse configurations of needle-type electrodes are commonly used to generate DC or AC corona discharges in various industrial applications. Previous studies confirm that the amount of charges generated by corona discharge is controlled by several factors such as the level of applied voltage, the ambient conditions, as well as the geometry of the electrode system. This paper aimed to evaluate the distribution uniformity of the charges generated by multiple-row needle-type electrodes and deposited on the Polyvinyl Chloride (PVC) plate surface, either at rest (“static” regime) or in motion (“dynamic” regime) under the corona electrode. The potential at the PVC plate surface was measured by a non-contact electrostatic voltmeter. The electric potential maps resulting from the experiments carried out in “static” regime, point out that the uniformity of the corona charging effect generated by the electrodes is related to their geometry and the level of the applied voltage. In the “dynamic” regime experiments, the surface potential profiles show that the distribution of electric potential on corona-charged polymer plates depends on the number of needles and the direction of movement under corona electrode system. Comparing the results obtained in this paper with the results obtained in previous studies, lead us to a general conclusion that the uniformity can be improved, to attain values higher than 95%, and this depends on the geometry of the electrode system and on the direction of the movement of the polymer plates in the electric field.

Materials degradation in non-thermal plasma generators by corona discharge

Atmospheric corona discharge devices are being studied as innovative systems for cooling, sterilization, and propulsion, in several industrial fields, from robotics to medical devices, from drones to space applications. However, their industrial scale implementation still requires additional understanding of several complex phenomena, such as corrosion, degradation, and fatigue behaviour, which may affect final system performance. This study focuses on the corrosive behaviour of wires that perform as a high-voltage electrode subject to DC positive corona discharge in atmospheric air. The experiments demonstrate that the non-thermal plasma process promotes the growth of the oxidative films and modifies the physicochemical properties of the materials chosen as corona electrodes, hence affecting device operation. Surfaces exposed to this non-thermal plasma are electrically characterized by negative exponential decay of time-depend power and analysed with SEM. Implications on performance are analysed and discussed.

Dividing and setting strategy of improving calculation efficiency for needle electrode corona discharge with a large‐scale space

Needle electrodes are widely used in the research of corona discharge. Aiming at the problem of needle electrode discharge in a large-scale space (tens or even hundreds of centimetres), a hybrid model was proposed in the previous work. However, its indispensable multiple iterations result in huge computation and further limit its wide applications. Therefore, a strategy to improve the computing efficiency by setting initial values in different computational domains is put forward in this work. Three types of setting initial values (global constant, partition constant and partition exponent) are simulated and compared in detail. The calculation results show that the calculation efficiency can be increased by 1.4 times simply through setting initial values of charged particles as different constants for the divided subdomains, and further be improved by 4.3 times by setting those in the ionization region as an exponential distribution. The extension of the proposed strategy has also been discussed under various voltages, which shows that the results under other voltages can be quickly obtained based on the fitted coefficients under a specific voltage, and the improvement can reach up to 10 times. The accuracy of calculated results has been demonstrated by a needle-plate electrode device with a vertical distance of 25 cm. This research provides an effective strategy for improving the computing efficiency of corona discharge in a large-scale space, and implies the potential in optimizing the analyses of complex electrodes.